Street gutters are oases of microscopic life - such as microalgae and fungi - that may help clean rainwater and urban waste by decomposing solid debris and pollutants, according to a study in France.

Street gutters are oases of microscopic life – such as microalgae and fungi – that may help clean rainwater and urban waste by decomposing solid debris and pollutants, according to a study in France. (Image Source:BOREA Biology of Aquatic Organisms and Ecosystems research unit)

Street gutters are oases of microscopic life – such as microalgae and fungi – that may help clean rainwater and urban waste by decomposing solid debris and pollutants, according to a study in France. Scientists from the BOREA Biology of Aquatic Organisms and Ecosystems research unit in France and Max Planck Institute for Terrestrial Microbiology in Germany have shown that Parisian street gutters are oases of microscopic life, home to microalgae, fungi, sponges, and mollusks.

Grouped into communities, these microorganisms may help clean rainwater and urban waste by decomposing solid debris and pollutants such as exhaust fumes and engine oil. A deeper understanding of the role and composition of these communities could help elucidate the services rendered by gutter ecosystems, researchers said. The findings, published in the ISME Journal, are the first to reveal the unsuspected biodiversity of microscopic life in Paris city streets.

Scientists from the BOREA research unit first suspected the presence of microalgae in Paris streets after noting the characteristic green or brown colour of gutter water and observing the presence of bubbles, which are the result of photosynthetic activity. The researchers analysed different samples of non-potable water from the Seine, the Ourcq Canal, curbside water outlets for street cleaning, and street gutters to identify the microorganisms they harboured.

The team identified 6,900 potential species of eukaryotes in the hundred or so samples of water and biofilms collected from every district of Paris. Diatomaceous microalgae make up a large part of this biodiversity. Other unicellular eukaryotes, fungi, sponges, and mollusks were also found. Even more astonishingly, analyses revealed that nearly 70 per cent of these species were not found in the non-potable water sources.

The profiles of these microbiological communities vary greatly between sampling sites, suggesting their origin may be associated with human activities or that the microorganisms have adapted to their specific urban environment. Hence, street gutters and the microscopic life they host appear to constitute a unique ecosystem with ecological roles still to be discovered, researchers said.